In a conventional mobile radiotelephone communications system, communications are provided between one or more mobile user terminals, a wired communications system, and the radiotelephone communications system. In other words, a radio link between a mobile user terminal and the radiotelephone communications system can be used to support communications between the mobile user terminal and a second mobile user terminal, or between the mobile user terminal and a telephone on the wired communications system.
When a call is placed to the mobile user terminal, the radiotelephone communications system sends an incoming call message to the mobile user terminal over a control channel indicating the presence of an incoming call. Upon reception of this incoming call message over the control channel, the user terminal and the radiotelephone communications system initiate a series of control communications to establish a link therebetween over a dedicated channel. If the user terminal is unavailable to receive the initial incoming call message, however, the telephone call may not be established.
Accordingly, a cellular radiotelephone communications system, such as the terrestrial Global System For Mobile Communications (GSM 03.38), may provide a voice mail feature allowing the calling party to leave a voice mail message for the user terminal if the telephone call is not established. In addition, GSM systems may provide a message to the user terminal indicating that voice mail has been received thereby alerting the user terminal to the presence of the voice mail so that the user can check the voice mail in a timely manner. In particular, the voice mail indicator message can be transmitted in a GSM system as a part of a Short Message Service (SMS) message.
Not all radiotelephone communications systems, however, support SMS messages. Furthermore, if the user terminal is unable to establish communications responsive to the initial incoming message (page), it may also be unable to receive the SMS message including the voice mail indicator.